Modern high volume package delivery systems often include package conveying systems that accept packages from one or more loading stations, and transport the packages to a variety of output destinations such as chutes, bins, and subsequent conveyor systems.
One of the most conventional types of conveyors is a belt conveyor, which includes the use of an endless flexible belt which passes over at least two cylindrical rollers, one of which is a drive roller. Packages are placed atop the upwardly-directed "working" surface of the belt conveyor, and are transported in a generally straight direction from end of the conveyor to the other. Another type of conveyor is a "roller" conveyor which con include powered or idling rollers which contact, support, and in certain instances propel the bottom of the package along its path.
Such prior art conveying systems tend to have a substantially fixed capacity which is a function of their operating speed. This translates to a certain number of cells or trays or linear feet of belt which pass a reference point. The higher the number the higher the capacity.
However, the effect of inertia limits conveyor speeds; the faster the conveyor speeds the more likely inertia will negatively affect discharge accuracy. At very high speed reliable control of the packages is very difficult due to the effect of inertia. A desired property of any automated system is operation accuracy which is very difficult to achieve at high constant speed. System mistakes are bound to be very costly to a user since it can lead to mis-deliveries of parcels which must be rectified at the carrier's expense.
Various prior art methods and apparatuses have been developed to convey items.
U.S. Pat. No. 3,799,319 to Cutler et al. discloses an article-aligning apparatus having a variable speed feed conveyor for providing articles to trays of a main sorting conveyor. The articles are aligned on the trays once they are placed on the sorting conveyor.
U.S. Pat. No. 4,765,456 to Bower discloses a variable speed belt conveyor with a drive system designed to share the load at any speed of operation.
U.S. Pat. No. 5,170,877 to Francioni discloses an automatic conveyor system. The conveyor system includes a main conveyor system and a plurality of branch conveyors. If a stoppage is detected at one of the branch conveyors and articles begin to accumulate on the other branch conveyors, the other branch conveyors begin to operate at a faster speed. The speed of advance of conveyor portion of a branch conveyor is varied in order to prevent overcrowding of articles on the conveyor.
U.S. Pat. No. 4,792,033 to Iwata et al. discloses an apparatus for supplying articles to a conveyor. The speed of the conveyor is varied so that articles are uniformly spaced on the conveyor. The conveyor speed is increased to produce space on the conveyor sufficient to receive a predetermined number of additional articles.
Therefore it may be seen that variable speed sorting conveyors are known in the art. Furthermore, increasing the capacity of a main sorting conveyor by increasing the speed of input conveyors is known. It is also known to accumulate articles at a particular location for entry onto the main sorting conveyor by varying the speed of a conveyor.
However, a need still exists in the art for an improved sorting conveyor.